Rabi Ranjan Chattopadhyay

In vitro antibacterial potential of Eugenia jambolana seed extracts against multidrug-resistant human bacterial pathogens.

The present study was carried out to evaluate the possible in vitro antibacterial potential of extracts of Eugenia jambolana seeds against multidrug-resistant human bacterial pathogens. Agar well diffusion and microbroth dilution assay methods were used for antibacterial susceptibility testing. Kill-kinetics study was done to know the rate and extent of bacterial killing. Phytochemical analysis and TLC-bioautography were performed by colour tests to characterize the putative compounds responsible for this antibacterial activity. Cytotoxic potential was evaluated on human erythrocytes by haemolytic assay method and acute oral toxicity study was done in mice. The plant extracts demonstrated varying degrees of strain specific antibacterial activity against all the test isolates. Further, ethyl acetate fraction obtained from fractionation of most active ethanol extract showed maximum antibacterial effect against all the test isolates. Phytochemical analysis and TLC-bioautography of ethyl acetate fraction revealed that phenolics were the major active phytoconstituents. Ethyl acetate fraction also demonstrated no haemolytic activity on human erythrocytes and no gross behavioural changes as well as toxic symptoms were observed in mice at recommended dosage level. The results provide justification for the use of E. jambolana in folk medicine to treat various infectious diseases and may contribute to the development of novel antimicrobial agents for the treatment of infections caused by these drug-resistant bacterial pathogens.

Evaluation of Synergistic Antibacterial and Antioxidant Efficacy of Essential Oils of Spices and Herbs in Combination

The present study was carried out to evaluate the possible synergistic interactions on antibacterial and antioxidant efficacy of essential oils of some selected spices and herbs [bay leaf, black pepper, coriander (seed and leaf), cumin, garlic, ginger, mustard, onion and turmeric] in combination. Antibacterial combination effect was evaluated against six important food-borne bacteria (Bacillus cereus, Listeria monocytogenes, Micrococcus luteus, Staphylococcus aureus, Escherichia coli and Salmonella typhimurium) using microbroth dilution, checkerboard titration and time-kill methods. Antioxidant combination effect was assessed by DPPH free radical scavenging method. Total phenolic content was measured by Folin-Ciocalteu method. Bioactivity –guided fractionation of active essential oils for isolation of bioactive compounds was done using TLC-bioautography assay and chemical characterization (qualitative and quantitative) of bioactive compounds was performed using DART-MS and HPLC analyses. Cytotoxic potential was evaluated by brine shrimp lethality assay as well as MTT assay using human normal colon cell line. Results showed that among the possible combinations tested only coriander/cumin seed oil combination showed synergistic interactions both in antibacterial (FICI : 0.25-0.50) and antioxidant (CI : 0.79) activities. A high positive correlation between total phenolic content and antibacterial activity against most of the studied bacteria (R2 = 0.688 – 0.917) as well as antioxidant capacity (R2 = 0.828) was also observed. TLC-bioautography-guided screening and subsequent combination studies revealed that two compounds corresponding to Rf values 0.35 from coriander seed oil and 0.53 from cumin seed oil exhibited both synergistic antibacterial and antioxidant activities. The bioactive compound corresponding to Rf 0.35 from coriander seed oil was identified as linalool (68.69%) and the bioactive compound corresponding to Rf 0.53 from cumin seed oil was identified as p-coumaric acid (7.14%) by DART-MS and HPLC analyses. The coriander/cumin seed oil combination did not show any cytotoxic effect both in brine shrimp lethality as well as human normal colon cell line assays. The LC50 in brine shrimp lethality assay was found to be 4945.30 μg/ml and IC50 in human normal colon cell line was > 1000 μg/ml. The results provide evidence that coriander/cumin seed oil combination might indeed be used as a potential source of safe and effective natural antimicrobial and antioxidant agents in pharmaceutical and food industries.

Anti-inflammatory, anti-lipid peroxidative, antioxidant and membrane stabilizing activities of hydroalcoholic extract of Terminalia chebula fruits

Abstract Context: Arthritis is inflammation of one or more joints. Terminalia chebula Retz. (Combretaceae) fruit is mentioned in Ayurveda as useful in treating arthritic disorders. Objective: This work was undertaken to evaluate the anti-inflammatory, antioxidant, anti-lipid peroxidative and membrane-stabilizing effects of hydroalcoholic extract of Terminalia chebula fruits and also to establish a possible association between them. Materials and methods: In vivo anti-inflammatory activity of T. chebula fruit extract at different doses ranged from 50 to 500 mg/kg, p.o. was evaluated against carrageenin-induced inflammation in rats. Human erythrocyte hemolytic assay was used for in vitro anti-inflammatory activity testing with 50 to 500 µg/ml fruit extract. Antioxidant potential of test fruit extract (10 to 100 µg/ml) was evaluated using TBARS and DPPH methods. The fruit extract was standardized for total phenolic content using Folin-Ciocalteu method. Results: The standardized extract at 250 mg/kg, p.o. dose caused 69.96% reduction in carrageenin-induced rat paw edema and demonstrated 96.72% protective effect on human RBC membrane stability. Besides, T. chebula fruit extract significantly reduced the in vivo formation of TBARS in carrageenin-induced rat liver with IC50 94.96 mg/kg, p.o. and also in vitro radical scavenging activities in DPPH assay method with IC50 42.14 µg/ml. The standardized extract contains phenolics 118.5 mg gallic acid equivalent/g of extract. Discussion and conclusion: These promising findings support the traditional use of T. chebula fruits in the treatment of arthritic disorders and suggest that radical quenching may be one of the mechanisms for its anti-inflammatory activity.

Efflux-pump inhibitory activity of a gallotannin from Terminalia chebula fruit against multidrug-resistant uropathogenic Escherichia coli

This study was carried out to evaluate the possible efflux-pump inhibitory activity of a gallotannin 1,2,6-tri-O-galloyl-β-d-glucopyranose isolated from Terminalia chebula fruit against multidrug-resistant (MDR) uropathogenic Escherichia coli. Susceptibility tests of antibiotics and ethidium bromide in the presence and absence of isolated gallotannin and phenylalanine-arginine β-naphthylamide (PAβN) were conducted by using the microbroth dilution assay. Ethidium bromide accumulation and efflux assays were performed spectrofluorometrically to elucidate the possible resistance-modifying activity of isolated gallotanin, if any. Minimum inhibitory concentrations of test antibiotics and ethidium bromide were reduced in the presence of isolated gallotannin and PAβN. The isolated gallotannin also demonstrated efflux-pump inhibitory activity against the studied bacteria as evidenced from ethidium bromide accumulation and efflux assays. The isolated gallotannin, 1,2,6-tri-O-galloyl-β-d-glucopyranose exhibited efflux-pump inhibitory activity which may be one of the possible mechanisms of its antibacterial action against MDR uropathogenic E. coli.

In vitro antimicrobial potential of Terminalia chebula fruit extracts against multidrug–resistant uropathogens

Abstract Objective Terminalia chebula Retz. (combretaceae) is called the “King of Medicine” in Tibet and is always listed at the top of the list of “Ayurvedic Materia Medica” because of its extraordinary power of healing. The present study was carried out to evaluate the possible in vitro antibacterial potential of different solvent extracts of T. chebula fruit against multidrug–resistant uropathogens. Methods A total of 52 multidrug–resistant uropathogenic bacteria were used in this study. Successive extractions of T. chebula fruits were performed with solvents of different polarities. Agar well diffusion and microbroth dilution assay methods were used for antibacterial susceptibility testing. Kill-kinetics study was done to know the rate and extent of bacterial killing. Qualitative phytochemical screening was done to know the major phytoconstituents present in the plant material. Acute oral toxicity study in mice was performed to evaluate the toxic potential of the plant material, if any. Results The ethanol extract of T. chebula fruits demonstrated a strong antimicrobial activity against all the test isolates and found to be most effective over others. Kill-kinetics study showed dose and time dependent antibacterial activity of ethanol extract. Phytochemical analysis revealed the presence of high concentration of phenolics and low concentration of flavonoids and terpenoids. In acute oral toxicity study, no gross behavioral changes were observed in mice at recommended dosage level and 24 h LD50 of ethanol extract was found to be >4 g/kg, p.o. in mice. Conclusions The results provide justification for the use of Terminalia chebula fruit in folk medicine to treat various infectious diseases and could be useful for the development of alternative/complementary medicine for multidrug–resistant uropathogens.

A comparative evaluation of antibacterial potential of some plants used in indian traditional medicine for the treatment of microbial infections

A comparative in vitro antibacterial potential of extracts (aqueous and ethanol) of five important medicinal plants (Aegle marmelos, Azadirachta indica, Terminalia chebula, Mangifera indica and Ocimum sanctum) were investigated using microbial growth inhibition assays against the common human pathogenic bacteria (Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli) of clinical origin. All the plant materials showed varying degrees of strain specific inhibitory action and ethanol extract of the plant materials showed higher antibacterial activity than their aqueous counterparts. Besides, T. chebula and A. marmelos had the strongest antibacterial activity out of which, T. chebula possessed a wider spectrum and a superior antibacterial potential over the others. The bioactive compounds of T. chebula might have potential as therapeutic agents for the treatment of common bacterial infections.

Isolation and identification of a gallotannin 1,2,6-tri-O-galloyl-β-D-glucopyranose from hydroalcoholic extract of Terminalia chebula fruits effective against multidrug-resistant uropathogens.

In this study, an attempt has been made to isolate and identify the bioactive compounds from hydroalcoholic extract of Terminalia chebula fruits effective against multidrug‐resistant uropathogens and also to elucidate the influence of metal ions on the growth inhibitory activity of isolated compounds against the studied bacteria, if any.

Synergistic antibacterial and antibiofilm efficacy of Nisin in combination with p‐Coumaric acid against foodborne bacteria Bacillus cereus and Salmonella typhimurium

The aim of the study was to evaluate possible antibacterial and antibiofilm efficacy of a bacteriocin, nisin with two essential oil components linalool and p‐coumaric acid in combination against food‐borne bacteria Bacillus cereus and Salmonella typhimurium. Their inhibition effects on planktonic cells and preformed biofilms were evaluated using microbroth dilution and checkerboard titration methods. Nisin/p‐coumaric acid combination showed synergistic effects against planktonic cells of both the studied bacteria, whereas nisin/linalool combination showed synergistic activity against B. cereus and additive effect against S. typhimurium. In preformed biofilms, nisin by itself failed to show >50% antibiofilm efficacy against both the studied bacteria, but in combination with linalool and p‐coumaric acid, it exerted >50% antibiofilm efficacy. On the basis of fractional inhibitory concentration indices values, nisin/p‐coumaric acid combination exhibited synergistic antibiofilm activity, whereas nisin/linalool combination showed additive effects against preformed biofilms of studied bacteria. The results provide evidence that p‐coumaric acid due to its synergistic interactions with nisin against planktonic cells and biofilms of both Gram‐positive and Gram‐negative food‐borne bacteria enhanced the antibacterial spectrum of nisin, which subsequently may facilitate their use in the food industry.

Synergistic antibiofilm efficacy of a gallotannin 1,2,6-tri-O-galloyl-β-D-glucopyranose from Terminalia chebula fruit in combination with gentamicin and trimethoprim against multidrug resistant uropathogenic Escherichia coli biofilms

In recent years the emergence of multiple drug resistance microbes has become a global public health problem. The aim of the present investigation was to evaluate possible antibiofilm efficacy of a gallotannin 1,2,6-tri-O-galloyl-β-D-glucopyranose from Terminalia chebula fruits alone and in combination with gentamicin and trimethoprim against preformed biofilms of multidrug-resistant (MDR) uropathogenic E. coli isolates using microbroth dilution, checkerboard titration and kill kinetics methods. Test gallotannin showed > 50% antibiofilm efficacy after 24 h when administered alone whereas gentamicin and trimethoprim failed to do so. But in combination, test gallotannin/gentamicin and test gallotannin/trimethoprim showed 71.24±6.75% and 93.4±8.46% antibiofilm activity respectively. On the basis of FICI values, test gallotannin/gentamicin showed synergistic interactions against 71.42% and test gallotannin/trimethoprim against 85.71% biofilm forming test bacterial isolates. Kill-kinetics study confirmed their synergistic interactions. Thus, gentamicin and trimethoprim in combination with test gallotannin may have potential for treatment of urinary tract infections caused by biofilm forming MDR uropathogenic E. coli.